One of the things I like about these old tractors is being able to fiddle with things like points. These old engines will usually start telling you they need service, LONG before they quit running. I get many emails that start something like, "my tractor was getting harder and harder to start, now it won't start at all". Why not fix it before the grass is a foot tall or it's snowing an inch an hour? Well, that's nice in theory, but out in the real world with professional procrastinators like me, maintenance often takes a back seat to essential activities like drinking beer and throwing darts. Ok, I haven't had a beer in many years, so don't even have that excuse.
Modern cars have spoiled us. We are losing the ability to pay attention. "Getting harder to start", means it's PAST time for maintenance. It is often impossible to say "the" problem is air cleaner, points, condenser, plugs, wires, cap, ignition switch, etc. By the time I get any "won't-start" tractor running again, I've fixed several things that could have been "the" problem. If you suspect points, it only takes a minute to check them on a side distributor engine. Maybe 2 minutes for a front distributor. You can try popping the front cap and using a mirror to get a look, but I'm going to just pull the front distributor, and take it to my workbench. If I'm working on a side distributor, I get something to sit on, or sit on the tire.
You should have an ignition point file in your tool box, on the tractor. This is a small, thin, flexible file, with a square tip that is easy to slip between the points. In fact, a good "point file" really isn't a file, it is a burnisher. The purpose is to clean and polish rather than remove material. If the points look discolored or wet, just running the file through them a few times is often enough to get a tractor started. Do this with the points closed, using normal spring tension to polish both contact surfaces at the same time. If this got the tractor started, mark it on your list to completely service the distributor as soon as possible.
While messing with the points, grab the end of the distributor shaft and see if there is any side play. Watch the points and see if the gap is changing while trying to move the shaft side to side. These engines are 50 to 70 years old. It might have been a L O N G time since the last distributor rebuild. New distributor bushings only cost around $10 each and most anyone can replace bushings. If the shaft is badly worn, you might need a new one. That's a little more expensive. If rebuilding is beyond your ability, rebuilt or new distributors are available. A sloppy distributor shaft is nothing but trouble. It needs to be fixed as soon as possible. Here are some links to my step-by-step distributor rebuild pages for the FRONT DISTRIBUTOR and for the SIDE OR ANGLE MOUNT DISTRIBUTOR
Check inside of distributor cap for dirt, moisture, or carbon tracking. Usually the cap can just be wiped out with a rag. Clean any deposits from the springy terminal on top of the rotor. Look at the end terminal of the rotor and the spark plug terminals inside the cap. Look for deposits or signs of actual contact. The end of the rotor should get close but never actually touch the terminals inside the cap. This is a high voltage system. A spark hot enough to jump the spark plug gap (under pressure in the cylinder) is plenty hot enough to jump a gap between rotor and distributor terminals. Back in the bad old days we could buy clear plastic distributor caps. It was really cool to watch the operation of the points and actually see sparks going to each spark plug wire. If it looks like the rotor has hit some of the spark plug terminals in the cap, check the distributor shaft bushings again.
There have been cases where a new rotor has hit terminals inside the distributor cap. This usually causes the distributor cap to crack or break completely apart. Replacement rotors and caps from the land of almost fits continue to cause problems. One suggestion is to buy a new cap and rotor at the same time from the same place. This should have a better chance that they will be a matched set. Even better, buy tractor parts from a specialty supplier such as just8ns.com. In some cases it may cost a little more for parts that appear to be identical, but the specialty suppliers have a much bigger incentive to maintain quality control of their parts inventory. Rejected stuff often ends up being bought for little or nothing and still ends up on local store shelves or is being sold cheap on-line. Buyer Beware Cheap Tractor Parts are exactly that, cheap parts.
We used to routinely replace points and condenser on cars. Tractors don't go nearly as many miles. There is much less wear and tear. Points and condenser can often remain in service on a tractor for several years. In fact. replacement parts have become such poor quality, we are often better off with the old parts. Look at the surface of the points. A magnifying glass may be required. If the surface looks smooth, the condenser is good, and the correct rating. Don't change the condenser unless there appears to be some other problem like rust. If the points are pitted and burned looking, replace the condenser. Carefully check the terminal for the condenser wire and where the points connect to the coil. These connections must be solid and completely insulated from other metal.
The correct point gap for a front distributor is 0.015". For a side distributor it is 0.025". After setting a million sets of points, I can tell just by looking at them if they are close enough to run, but I'm still going to use the proper size feeler gauge to set them as close as possible to perfect. The wire type gap gauges are easier to use, but a flat type feeler gauge can be just as accurate.
Looking at the guts in the distributor, the points are bolted to a flat plate under the rotor. The rotor should easily pull straight off. If this is a side distributor engine, watch out for a small spring clip. The clip should stay on the distributor shaft but may get stuck inside the rotor. Don't lose that clip! The spring clip is what keeps the rotor tight. The distributor shaft has a flat spot that corresponds to the hole in the rotor, so the rotor only fits one way.
If you have the front distributor on your work bench, ignore this paragraph. For side distributor engines, make sure the tractor is in neutral, then bump the starter until it stops with the points open. It is ideal when the high point on the distributor cam stops right on the rubbing block of the points. The mechanical advance in the distributor will allow the distributor shaft to be turned slightly if it stops just a little short of the peak. The distributor has a mechanical advance mechanism under the plate. No need to remove the plate to look at the mechanism, unless you are rebuilding the distributor.
With the front distributor, we avoid all this messing around. We take teh distributor to the workbench and just turn the distributor shaft anywhere we want it. Once we have the rubbing block sitting on a point of the distributor cam, check the gap between the two pieces of contact material. What we are measuring is the maximum distance the distributor can open the points as it turns.
If we are replacing the points, they are held to the plate in the distributor by a screw at each end of the fixed point bracket. Ignore the screw in the middle of the point strap on the front distributor. That is a special eccentric screw that is used when adjusting the points. The side distributor does not have this simple eccentric screw adjuster, the side distributor has a notch in the points that can be pried with a flat blade screwdriver to help set the gap.
Before we get all excited and install the new points, look carefully at them. Many of the replacement point sets are not made very well. Look at how the two pieces of contact material come together when they are closed. Do they come together square and centered? If not, you may need to bend them slightly to correct the error. Sad that quality has deteriorated to the point we have to tweak new parts. Be careful where and how you bend them. I clamp the base in a vise and use a short pair of needle nose pliers to carefully bend the fixed side mounting tab into alignment. If the points are not aligned properly, there will be less surface area to transfer current, and they will soon be pitted and burned. Finally, I make a few passes with a point file between the two contact faces to make sure they are filed parallel, and to remove any manufacturing glaze that would prevent them from working.
Now, install the points in the distributor, but leave the mounting screws just barely touching, so the plate can still move. On the front distributor, the eccentric bolt can now be turned to "set" the proper gap. With the side distributor we have to manually pry the points until the gap is correct. Tighten the screws and re-check the gap. It probably moved a bit. Loosen the screws and try again. If the points closed a bit, try starting with a little too much gap. It often takes several whacks, but this has to be done correctly. Almost right, isn't good enough, if we want the engine to run well.
If the points screws are stripped and will not hold tight, the fix is to replace with a slightly larger diameter screw. The replacement will be a very short length #8-32 screw. That length should not be more than 3/16" or it will interfere with the rotating advance weights below the top plate. If your top plate already has the larger screws, it's time for a new top plate assembly. If you only have screws that are too long, look at a pair of wire strippers. Most have a series of threaded holes near the hinge. Find a hole for the #8-32 screw, twist the screw into the threaded side until the part that is too long comes thru the unthreaded side. Snap the screw off, and let the threaded part fix that last thread as the shortened screw is backed out.
This page was getting a little long, so I broke out the more detailed front and side distributor information at the following links.
FRONT DISTRIBUTOR DETAILS
All Ford-Ferguson 9N, 2N, and Early Ford 8N
SIDE DISTRIBUTOR REBUILD
Late Ford 8N (50-52)
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